Single Molecule: Detection and Manipulation

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Single Molecule Detection and Manipulation
Joel Stavans group
Jaffar Ali Ido Braslavsky Roee Amit

• Interaction Between
• Membranes and Polymers

• Ilan Tsafrir Tamar Arzi

Physics of Complex Systems - Weizmann
Institute of Science
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Single Molecule Detection and Manipulation
(Ensemble (1018) ltgt Single molecule
(100 Averages ltgt Dynamics,
Individual behavior
Tools

• Optical Tweezers
• Confocal fluorescence microscopy
• Evanescent illumination
• Molecular biology techniques

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Optical Tweezers
Force (pN)
Small particles (micron
scale) can be trapped by the
intensity gradient of focused
light
F-a(?E)2
Noninvasive Techniques in Cell Biology 375
(1990)
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Pulling on a DNA moleculewith Optical Tweezers
Bead
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? DNA Force - Extension Curve
Approximation of the Worm-like Chain Model
prediction
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Single Molecule Detection and Manipulation

• Looping of DNA
• Opher Gileadi (Weizmann, Molecular Genetics)
• Stephen Quake (Applied Physics, Caltech)
• Collapse of DNA
• Stephen Quake
• Single Molecule Enzymatic Activity
• David Bensimon (ENS, Physics)

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Transcription Regulation by looping of DNA
DNA
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Looping of DNA
Spontaneous
Gelles, Science 267378 (1995)
Looping dynamics Time scales of bound and
unbound states Dependence on length Dependence
on Persistence length
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Looping - influence of bending protein
IHF
IHF
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IHF - Integrating Host Factor This protein
induces a U-Turn in DNA IHF - blue/red DNA -
green/yellow
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Evanescent Illumination
Microscope Objective
Bead
Bead
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Summary

• Macromolecules are interesting as a complex
  physical system while understanding their
  physical properties could contribute to the
  understanding of their function as a biological
  ingredient.
• The experimental tools enable us to monitor and
  manipulate single molecules.